To make an integrated circuit, various material layers are patterned using a photolithography process. The photolithography process includes photoresist (resist) coating, exposing and developing. Currently, when forming a resist patterning on wafer substrate having a material layer, such as metal film, the substrate can be etched by wet chemical. Additional rinse may be applied thereafter.
However, the current wet chemical etch has various issues. The wet chemical etch cannot have good etch selectivity between and significant lateral etch. In other words, the film underlying the resist pattern is substantially etched away without resist protection. This may further cause resist peeling. In addition, the resist pattern cannot be properly transferred the underlying film due to the lateral etch. The wet chemical etch cannot have good etch rate control since the etch rate is too high even the etchant concentration is dilute or temperature is reduced. This further worsens the lateral etch issue. The wet etch chemical has high penetration capability, such as by capillary force, and is able to penetrate into the interface between the resist and the material layer on the substrate. Such chemical penetration could also cause resist peeling and unexpected etching effect to the material layer underlying the resist pattern.